SWODY1
SPC AC 230559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT MON MAR 23 2009
VALID 231200Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTERNOON INTO TONIGHT
FROM NORTH CENTRAL-NERN OK INTO PARTS OF ERN KS...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
FROM N TX/OK THROUGH THE CENTRAL PLAINS/WRN MO TO SRN-SERN SD AND
SWRN MN...
...SYNOPSIS...
A DYNAMIC LARGE-SCALE PATTERN WILL EXIST OVER THE CENTRAL CONUS ON
DAY 1 AS AN INTENSE MID/UPPER-LEVEL LOW SHIFTS NEWD FROM THE CENTRAL
HIGH PLAINS INTO SD/NEB. AS THIS PROCESS OCCURS...SIGNIFICANT
HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT WILL SPREAD ENEWD THROUGH
THE CENTRAL/SRN PLAINS...AND EVENTUALLY MORE NEWD THROUGH THE
DAKOTAS INTO UPPER MS VALLEY. STRONG WSWLY MID AND UPPER LEVEL FLOW
WILL SPREAD EWD INTO KS/SRN PLAINS BY THIS AFTERNOON...WITH A LEAD
MID LEVEL JETLET TRACKING NEWD ACROSS NRN KS/NEB WITH THE EJECTING
UPPER LOW.
IN THE LOW LEVELS...STRONG CYCLOGENESIS IS EXPECTED TO BE UNDERWAY
ACROSS NERN CO AT 12Z TODAY. THIS LOW SHOULD UNDERGO SOME DEEPENING
THIS MORNING AS IT TRACKS NEWD INTO CENTRAL NEB...AND THEN BEGIN TO
FILL FROM LATE THIS AFTERNOON INTO TONIGHT. THE LOW IS PROGGED TO
REACH SERN/ERN SD BY 12Z TUESDAY. A TRAILING COLD FRONT WILL MOVE
ENEWD ACROSS NEB/NRN KS DURING THE FIRST HALF OF THE PERIOD.
MEANWHILE...A DRY LINE WILL MIX EWD REACHING CENTRAL KS TO WRN OK BY
EARLY-MID AFTERNOON. THE AFOREMENTIONED COLD FRONT WILL MOVE ESEWD
ACROSS KS/SRN HIGH PLAINS FROM LATE AFTERNOON THROUGH TONIGHT...AND
SHOULD EXTEND FROM WRN IA...WRN MO SWWD THROUGH CENTRAL OK TO SW TX
BY 12Z TUESDAY.
...NRN KS/NEB INTO MID MO VALLEY...
FORCING FOR ASCENT WILL SPREAD NEWD ACROSS THE CENTRAL PLAINS
ATTENDANT TO A LEAD MID LEVEL IMPULSE ACCOMPANYING THE MID/UPPER
LEVEL LOW/TROUGH. SURFACE HEATING IS EXPECTED AHEAD OF THE COLD
FRONT ACROSS SWRN/SOUTH CENTRAL NEB THIS MORNING INTO THE EARLY
AFTERNOON. ALTHOUGH LOW LEVEL MOISTURE WILL BE MODEST /SURFACE
DEWPOINTS IN THE LOWER 50S...THE SURFACE HEATING COMBINED WITH COLD
MID LEVEL TEMPERATURES/STEEP LAPSE RATES ATTENDANT TO THE UPPER LOW
WILL RESULT IN MLCAPE UP TO 500 J/KG. MODELS SUGGEST INITIAL
SURFACE BASED STORMS SHOULD DEVELOP BY EARLY AFTERNOON ACROSS
CENTRAL/SRN NEB AND ADJACENT NRN KS ALONG TRACK OF THE SURFACE LOW.
THIS ACTIVITY SHOULD THEN SPREAD ENEWD INTO THE MID MO RIVER VALLEY
AS DEEP LAYER ASCENT WEAKENS THE CAP OVER THIS REGION AND THE COLD
FRONT PROGRESSES ENEWD OVERTAKING THE PRE-FRONTAL TROUGH/DRY LINE.
HAIL/DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREATS
ACROSS THIS REGION. HOWEVER...THE SETUP WILL BE FAVORABLE FOR
LOW-TOPPED SUPERCELL DEVELOPMENT ALONG TRACK OF SURFACE LOW WHERE
ISOLATED TORNADOES ARE POSSIBLE. RAPIDLY BACKING DEEP-LAYER SHEAR
VECTORS WITH TIME ACROSS NEB INTO NRN KS SUGGESTS THAT STORMS MAY
EVOLVE INTO A LINEAR SYSTEM WITH THE THREAT FOR HAIL AND DAMAGING
WINDS CONTINUING EWD THROUGH THE MID AND LOWER MO VALLEYS MONDAY
NIGHT.
...CENTRAL KS/WRN MO SSWWD TO OK/RED RIVER VALLEY...
A CAP EXTENDING FROM CENTRAL/SRN KS SWD THROUGH THE RED RIVER VALLEY
IS EXPECTED TO LIMIT TSTM DEVELOPMENT UNTIL MID-LATE AFTERNOON.
INITIAL ACTIVITY SHOULD OCCUR ACROSS CENTRAL/SRN KS BETWEEN 21-00Z
AS THE COLD FRONT BEGINS TO MERGE WITH THE DRY LINE...AND FORCING
FOR ASCENT SPREADS EWD INTO SRN KS/OK ATTENDANT TO A SECOND LOBE OF
VORTICITY/FORCING FOR ASCENT WITHIN LEFT EXIT REGION OF MID/UPPER
LEVEL JETS. ADDITIONAL DEVELOPMENT WILL TAKE PLACE WITH SWD EXTENT
INTO NRN OK BY 00Z AS THE COLD FRONT CONTINUES TO OVERTAKE THE DRY
LINE...WITH TSTMS EXPECTED TO DEVELOP INTO WRN MO MONDAY EVENING AND
SWD TO THE RED RIVER LATE IN THE PERIOD.
THE QUALITY OF MOISTURE RETURN...EVEN INTO THIS REGION...SHOULD
REMAIN MODEST WITH SURFACE DEWPOINTS EXPECTED TO BE IN THE MID-UPPER
50S. THIS COMBINED WITH SURFACE HEATING AND STEEP MID LEVEL LAPSE
RATES REACHING THIS AREA BY LATE AFTERNOON WILL RESULT IN MLCAPE UP
TO 1000 J/KG FROM SRN KS INTO CENTRAL OK. THE ORIENTATION OF DEEP
LAYER SHEAR VECTORS MORE NORMAL TO THE SURFACE BOUNDARIES SUGGEST
THE POTENTIAL FOR BROKEN LINE SEGMENTS OR DISCRETE STORMS FROM THIS
AFTERNOON INTO TONIGHT. STRONG FLOW ALOFT WILL PROMOTE FAST STORM
MOTIONS /NEWD AT 40-50 KT/. STRONG SLY LLJ /50+ KT/ EXTENDING NWD
FROM OK WITH FURTHER STRENGTHENING TONIGHT WILL PROMOTE LARGE CURVED
HODOGRAPHS AND SUPPORT A THREAT FOR TORNADOES...SOME STRONG /IN THE
MODERATE RISK AREA/. HAIL AND DAMAGING WINDS WILL ALSO ACCOMPANY
THE SEVERE THREAT ACROSS THIS PORTION OF THE SLIGHT RISK AND
MODERATE RISK AREAS.
..PETERS/GARNER.. 03/23/2009
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment